The present invention relates, in general, to mold presses and, in particular, to a mold press force equalizer.
There are many forms of mold presses known in the art, such as those described in U.S. Pat. No. 4,576,092 assigned to Kohtaki & Co., Ltd. A mold press consists primarily of fixed and movable platens, upper and lower mold plates, a pressing/driving means, and an extruder. When the pressing/driving means exerts a force on the movable platen, the mold plates are forced together between the movable and fixed platens. An extruder then extends into one of the molds and forces plastic, or the like, under pressure into the mold cavities to encapsulate semiconductor devices, or the like.
The '092 patent describes a "Uniform-Pressure Press Apparatus" having a fluid filled cavity in one, or both, of the platens. This is used to distribute the pressure evenly across the load. This even distribution is a key in limiting, and eliminating, flash caused when some of the extruded material escapes between the mold plates. A major drawback of the device described in the '092 patent is its inflexibility. The area of the fluid filled cavity will dictate the size and dimension of the mold cavities and runners. This would limit the effective use of the apparatus.
In addition, mechanical and maintenance problems can result from having the force equalizer located within the platens of the press.
Accordingly, it is an objective of the present invention to provide a mold press force equalizer that overcomes the above deficiencies.
A further object of the present invention is to provide a mold press force equalizer which is not a portion of the mold platens.
Another object of the present invention is to provide a mold press force equalizer which allows independent design of the mold plates.
Still another object of the present invention is to provide a mold press force equalizer which may be used in existing mold presses.
The above and other objects and advantages of the present invention are provided by the mold press force equalizer described herein.